388 oenithoehynchidj!. claws, the anterior broad and blunt, the posterior compressed and pointed. Beak smooth, evenly rounded, its junction with the head marked, both above and below, by a projecting leathery flap, evidently developed to save the face from injury when the head is plunged in mud or gravel. Beak, excluding the flap, rather shorter than the rest of the head. Skull as already described. Horny plates two in number on each side of each jaw ; but the anterior are far less prominent and markedly specialized than the posterior. The former are long and narrow, and each forms a single longitudinal horny ridge, some 13 to 18 miUim. in length, which is placed on the side of the palate about 10 or 15 mUlim. from its feUow, and with its anterior point about level with the hinder end of the dumbbell-shaped bone. The surface of the bone beneath these plates-is quite smooth, and not modified in any way for their support. The poaterior plates are situated just below the level of the orbits, and each consists of a single broad horny and cuspidate plate, subdivided by transverse ridges into a small antero- internal and two large posterior portions. In the lower jaw the plates have the same shapes as in the upper, except that the anterior are longer, and that the posterior have their smaUest subdivision behind instead of in front. The bone below the posterior plates, both above and below, is broadened and excavated for the reception of their projecting cuspidate bases. Vertebrse:—Cervical 7, dorsal 17, lumbar 2, sacral 2, caudal 20 or 21 ; total 48 or 49. Habits. Aquatic, fossorial; feeding on water-insects, Crustacea, moUusca, &o. Range. That of the only species. There appears to be no reason to suppose that there ia more than a single species of Ornithorhynchus, the marked difference in size between the sexes and a certain variability in colour and texture of fur being apparently responsible for the considerable number of names that the common species bears. 1. Ornithorhynchus anatinus. Platypus anatinus, Shaw, Nat. Misc. x. pis. 385 & 386 (animal, beak, &c.) (1799); id. Gen, Zool. i. pt. i. p. 229, pis. 66 & 67 (animal &o.) (1800) ; Turt. Linn. S. N. i. p. 30 (1806); Oerrard, Cat, Bones Mamm, B, M. p. 288 (1862); Ch-ay, P. Z, 8. 1865, p. -886; id, Handl, Edentates, p. 29 (1878). Ornithorhynchus paradoxua, Blumenb. Voigt's Mag. Naturk. ii, p, 205 (1800); Home, Phil. Trans, 1800, p, 432, pla. xviii. & xix. (beak, skull, &c.); id, op. cit, 1802, p, 67, pis, ii,-iv, (anat,); Calkoen, Nat, Verh, Bat, Maatsch-Wet. ii. pt. i. p. 177 (1808); Desm. N. Diet. d'H N. (1) xxiv,, Tabl, MUh, p. 27 (1804); Blumenb, Abbild. Nat. Oegenst. no. 41 (animal) (1810); O. Fisch. Zoogn, in. p. 689 (1814); G. Cuv, R, A. i, p. 227 (1817); F, Cuv. Dents Mamm. p. 202, pl, Ixxxin, (horny plates) (1825); E. Oeoff.